Theoretical regression coefficients of Eq. 6 for the four models
| Model | Details | a | b | c | d |
|---|---|---|---|---|---|
| I (world-centered) | Full eye–head compensation | 1 | −1 | −1 | 0 |
| II (head-centered) | Eye-only compensation | 1 | 0 | −1 | 0 |
| III | Head-only compensation | 1 | −1 | 0 | 0 |
| IV (retinocentric) | No compensation | 1 | 0 | 0 | 0 |